Means for controlling hydraulic presses



Sept. 18 1923. 11,468,6(115 w. F. MAYER MEANS FOR CONTROLLING HYDRAULICPRESSES Filed Nov. 12, 1919 2 Sheets-Sheet 1 INVENTOR.

m2 e Z W BY 5 mar 4 70" A TTORNE Y.

Sept. 18, 1923.. nmww W. F. MAYER MEANS FOR CONTROLLING HYDRAULICPRESSES Filed Nov. 12 1919 2 Shaefics-Sheet 2 ffg4 Gm: ucq

Patented Sept. 18, 11923..

UNHTED STATES earner oeieiee.

WALDEMAR F. MAYER, 0F PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO TAYLOR-WHARTON IRON AND STEEL COMPANY, OF HIGH BRIDGE, NEW JERSEY, A COR-PORATION OF NEW JERSEY.

MEANS FOR CONTROLLING HYDRAULIC PRESSES.

Application filed November 12, 1919.

To all whom it may concern Be it known that I, VALDEMAR F. MAYER, acitizen of Switzerland, residing at Philadelphia, in the county ofPhiladelphia and State of Pennsylvania, have invented certain new anduseful Improvements in Means for Controlling Hydraulic Presses, of whichthe following is a specification.

This invention relates to a controlling means for hydraulic presseswherein the dead weight or additional live weight has a tendency to varythe set position of the press due to leakage loss of the motive fluid.

In presses of this type, the moving parts have a certain weight andfriction-resistance, and in raising the ram the fluid pressure has to beincreased to overcome these counter-pressures, while in lowering the ramthe fluid pressure has to be decreased as a compensation. If, however,there is the slightest lakage in the motive fluid acorresponding-decrease of operating pressure results, an a movement ofthe ram is had in correspondence with such pressure loss. It has beenproposed to utilize the movement of the ram, incident to such pressurelosses. to automatically start the pressure pump to restore the pressurethe return of the ram to set position automatically cutting out thepump. This means of control is objectionable, in that an actual movementof the ram is necessary to start the pump, arid this movement willloosen the grip on the work-piece, and in the case of a horizontal rampermit the work piece to fall out.

It is therefore highly desirable to provide means to take care of thepressure reduction due to leakage losses, without permitting anymovement of the ram from set position, and in the present invention,such means is directed toan auxiliary pressure pump to maintain aconstant pressure in the press cylinder, say equivalent to thesuspension pressure of the ram. so that any loss due to leakagefollowing the zero delivery position of the main pump, would becorrected as it occurred by the auxiliary pump pressure. and no possiblemovement of the ram could occur.

In the drawings Fig. 1 is a view in elevation, partly in Serial No.337,427.

section. showing the improved control means applied to a hydraulicpress.

Ifig. 2 is an enlarged side elevation of the main and auxiliary pumpsand connected parts.

Fig. 3 is an enlarged sectional view of the control valve.

F g. 4 is an enlarged sectional view, illustrating a conventional formof the main pump.

The invention is here Shown as applied to a hydraulic press, including aplaten 1, guided by uprights 2, and operated by a ram 3, drlvcn by themotive fluid in a cylinder 4. The motive fluid is delivered from astorage tank 5, through a pump 6, hereinafter termed the mam pump, andfrom the pump to the cylinder 4, through a. pipe 7. The main pump ispreferably of the reversible flow, variable delivery type, a lever 8,controlling the pump, such, for example as illustrated conventionally inFig. 4. This particular type of pump is well known in the art. and noclaim is made herein as to any particular construction thereof. Thelever 8, in the position shown. controls the main pump to maintain thepump at zerodelivery point, the extreme opposite positions of the lever,as indicated. setting the pump for maximum flow in reverse directions.that is to raise the'ram, or to lower the same.

lVith the main pump at zero delivery, any leakage loss. correspondinglyreduces the pressure in the ram cylinder 4, and a corresponding movementof the ram results. To avoid this loss of pressure, notwithstanding aleakage loss in the main pump.

as here shown is positively and continuously operated from the pumpshaft 10, which is in turn driven from a prime motor 11. The pump 9 isof ordinary single delivery rotary type. and being well known in the artrequires no particular description or illustrar tion herein.

The auxiliary pump, which is continuously driven, takes the motive fluidfrom the tank 5, through a connection 12, and delivers the same througha pipe 13 to the pipe 7 beyond the main pump. A check there is providedan auxiliary pump 9, which valve 14 is arranged in the pipe connection13, and set to open under pressure from the auxiliary pump, but ofcourse held closed when the pressure from the main pump in pipe 7exceeds the auxiliary pump pressure. A by-pass pipe connection 15 leadsfrom the pipe 13 beyond the auxiliary pump to the tank 5, and in thisby-pass is arranged a control valve 16. The valve 16 includes a casing17, formed with a valve seat for a valve 18, opening toward the tank. A.spring 19, hearing between the valve 18 and a washer 20 on the valvestem 21, is arranged for manual tension adjustment through a plug 22,bearing on the washer 20 and threaded into the casing 17 A hand wheel23, or other means is provided 'for adjusting the plug, and therebyvarying the tension on the valve.

If the pressure of spring 19 is set for the suspension pressure of theram, it will require such pressure to open the by-pass from theauxiliary pump to the tank 5, and

' through this control the desired result is obtained. When the mainpump is operating the pressure in pipe 7 will exceed the pressure inpipe 13 from the auxiliary pump, and the fluid from such auxiliary pumpwill by-pass to the tank. \Vith the main pump in zero delivery position,the motive fluid is held under the set pressure in the pipe 7 and ramcylinder. As neither of these parts, including the main pump, can beabsolutely fluid tight, pressure loss due to leakage is certain tooccur. But, if such leakage loss reduces the suspension pressure of theram, or would tend to such reduction, the pressure of the auxiliaryprovides a constant source of fluid pressure to the ram cylinder atsuspension pressure. Excess fluid from the auxiliary pump will by-passto the tank, but the control valve will constantly maintain the deliveryfrom the auxiliary pump of the suspension pressure, providing thecontrol valve is set for such pressure, as is contemplated.

The control means described provides, therefore, a constant pressure,always available, to maintain the active pressure at a predeterminedlimit, to thereby automatically take care of leakage losses andconsequent otherwise loss of pressure. This sustained pressure willtherefore absolutely prevent any movement of the ram, and will maintainthe set position irrespective of leakage losses.

Having thus described the invention, what is claimed as new, is

1. A control means for hydraulic presses, comprising a constantauxiliary pressure means including an adjustable valve to maintain themain set pressure constant against leakage losses.

2. A control means for hydraulic presses to avoid variation in the mainpressure in the set position of the press under leakage losses,comprising a constant auxiliary pres sure for the press equal to the setpressure, and means for controlling the pressure limit of such auxiliarypressure.

A control means for hydraulic presses for maintaining main set pressureconstant against leakage losses, comprising an auxiliary pressure means,and an adjustable'valve for holding such auxiliary pressure at anypredetermined set pressure limit for press control.

4. A control means for hydraulic presses for maintaining the main setpressure constant against leakage losses, comprising an auxiliary pumpfor delivering a fluid under pressure to the press, and a valve formain- ,taining the auxiliary pump pressure delivered to the pressconstant.

5. A hydraulic press, a main pressure pump therefor, means for settingthe pump at zero delivery to maintain the press under a set pressure,and auxiliary means for maintaining the set pressure of the pumpconstant against leakage losses.

6. A hydraulic press, a main pressure pump adapted when set at zerodelivery to maintain the press at set pressure, an auxiliary pump tomaintain the set pressure of the press constant under leakage losses,and a valve for controlling the pressure limit of the auxiliary pump inits eflect on the set pressure.

7 A hydraulic press, a main pump therefor, a storage tank for the mainpump, means for controlling the pump to maintain a set pressure on thepress, an auxiliary pump for delivering a constant pressure from thetank to the press, a by-pa'ss from between the auxiliary pump and tank,and a manually adjustable valve for controlling the by-pass, whereby anypressure of the auxiliary pump to the limit of the valve-set will bedelivered to the press.

In testimony whereof I afiix my signature.

WALDEMAR F. MAYER.

